Miniature multi-turn variable resistor



2 Sheets-Sheet 1 H. L. KRUSE EIAL MINIATURE MULTI-TURN VARIABLE RESISTOR June 30, 1964 Filed July 3, 1963 m BS BS WIL QQ QS S .NnN-P n Tlm. S

June 30, 1954 H. L. KRusE ErAL 3,139,601

MINIATURE MULTI-TURN VARIABLE RESISTOR Filed July 3, 1963 2 Sheets-Sheet 2 u Q` b S s Y INVENTORS HA/aow L. Knus, W/u. IAM H. KING, W/Lue 7.' HARD/50M Reeser L. 10A/55 United States Patent "O 3,139,601 MINIATURE MULTI-TURN VARIABLE RESISTOR Harold L Kruse, William H. King, Wilbur T. Hardison,

and Robert L. Jones, Riverside, Calif., assignors to Bourns, Inc.

Filed July 3, 1963, Ser. No. 292,625

\ 19 Claims. (Cl. 338-143) The invention hereinafter kdisclosed pertains to very small variable resistors characterized by fine resolution, capability of being mounted on a panel in a small extent of panel space, and immune to damage from attempts to drive the adjusting mechanism beyond the range of the resistor. More particularly the invention pertains to very small variable resistors of the potentiometer type utilizing a resistance element of helical coniiguration and comprising a plurality of convolutions of the element between the electrical ends or terminals of the element.

The necessity and desirability of providing electronic and other components characterized by smallness of physical size, very low weight, extreme reliability under adverse environmental conditions such as heat, vibration, shock and the like, and ability to endure abuse without adverse deterioration, are well known, especially in the aerospace industry. However, the several desired ends place somewhat inconsistent demands upon physical structures. For example, desired reduction of size and/ or of weight may result in a structure incapable of successfully enduring physical abuse. Similarly, attainment of a desired degree of stability in hot environments may dictate a wire-wound resistance element, which may require a considerable amount of space if a reasonable degree of resolution is to be attained; As the physical dimensions of a potentiometer, for example, are reduced, the principal structural components reach dimensions at which they are incapable of withstanding stresses incident to severe vibration or even ordinary operation; and space for the resistance element and operating mechanism is consequently at a premium.

The invention herein disclosed provides a variable resistor of the potentiometer type, capable of use as a rheostat or as a potentiometer, which is very small and compact but which is very rugged and may comprise a wire wound resistance element of considerable length to provide a high degree of resolution. By their construction variable resistors according to one embodiment of the present invention are capable of being eiectively mounted in groups in a compact array of tiers and layers without waste of intervening space, may be mounted on and supported by a console panel, and are adapted to be adjusted by servomotor means or manually without danger or damage incident to attempts to adjust the resistor beyond the prescribed limits of adjustment. Also byvirtue of the construction, the electrically-active parts or components are Well insulated; and the structural arrangement is such that the principal structures are not only very strong but utilize available space with a high degree of efficiency.

Variable resistors of the type here of interest, namely, such as utilize a helical resistance element of several convolutions or turns and are very small, typically have the resistance element and operating or adjusting mechanism housed in a generally cylindrical case or housing, and have a helical element on a centrally disposed stud or support and operating devices movable therearound, or alternatively have the resistance element aiiixed to the interior wall of the relatively thick cylindrical case and have the operating parts such as a slider and return bus bar disposed on a shaft disposed along and rotatable around the longitudinal axis of the helical element. In both constructions much of the space next-adjacent to and 3,139,601 Patented June 30, 1964 In the present invention, the helical resistance elementk is aflixed to the interior wall of the housing, the operating parts are rotated by a generally tubular or hollow carriage which replaces the usual shaft, and the space along the axis of the element is utilized for a return bus or conductor. Further, the housing is made of rectangular (square) cross-section, whereby the housing wall inter-V mediate the corners of a cross-section may be made much thinner than that of a cylindrical housing for the same element, to conserve space, and whereby the housing wall adjacent the four longitudinally-extending corner portions of the housing may be thick and provide a very rigid and strong structure with a minimum occupancy of space and of light weight. Further, according to the invention the generally slotted tubular rotatable rotor or carriage, whose principal function is to rotate a contact-carrier or slider device, is made thin but of relatively large diameter (nearly as great as the internal diameter of the resistance-element helix) and thus is made strong and rigid and easily capable of transmitting the torque required for operating the slider device. The slider device' or contact-carrier is mounted for sliding movement in longitudinally-extending slots or apertures formed in the tubular carriage, and thus may not only be small but does not require the usual large space between the rotor (carriage) and the resistance element. Thus the outside diameter of the tubular carriage may be made larger than otherwise would be possible. Also, due to the slider being mounted to slide along the longitudinal slots in the carriage device and largely Within the confines of the latter, and the return bus or conductor being located along the axis of the instrument, no space outside the rotor or carriage device is required for the bus bar, whereby a very compact variable resistor of small transverse dimensions is produced while concurrently permitting ernployment of a long resistance element for the sake of good resolution, all without making the resistor large or heavy.

The dimensions of the variable resistor being small, there is increased danger of damage to moving parts or the resistance element when an attempt is made to drive the slider device, or contacts, outside the established range of adjustments, that is, beyond the ends of the resistance element. Since the variable resistor, or at least the movable parts therein, are not visible to an operator during manual adjustment of the resistor, and since due to the very small size of the unit the torque required to effect rotation of the adjustable parts is of very low order, it is relatively easy to continue to apply torque after either end of the range of adjustment has been reached. Similarly, in those instances in which the adjustment is eifected by means of an electric motor, the latter may readily attempt to overdrive the adjusting mechanism, that is, drive the adjusting means beyond the range of adjustment, in either direction. It is usual in multi-turn rotary adjustment potentiometers to provide stop devices so arrangedjthat forward motion of the rotor or carriage is arrested as the end of the adjustment range is reached. Due to the very small size of the variable resistor herein disclosed it is possible to easily apply to the adjustment means such an excess of torque that such stops, or a part or parts of the adjusting mechanism, may be broken or damaged. To prevent the possibility of any such occurrence, yielding means of the nature of a clutch are provided in the rotary driving device or connection by means of which torque is transmitted from the driving motor (or the driving tool in the hand of an operator).

rg The yielding means, hereinafter termed a clutch for convenience, is appropriately composed of two arrays or sets of cooperating elements one set of which is conveniently provided as an integral part of a one-piece rotary carriage or rotor whose functions have been previously indicated. The other set of the cooperating elements is conveniently provided as parts of a plural-limbed spring that is secured to and rotated by a shaft-like element forming a second part of a driving device and which shaft is. conveniently housed for rotation in a means providing one end of the Variable resistor and by means of which the resistor is mounted on a panel or the like.

The preceding brief general description of the invention indicates that it is a broad general object of the invention to provide improvements in helical-element variable resistors.

Another object of the invention is to provide a very small strong variable resistor of the helical-element type.

Another object of the invention is to provide improvements in the structural arrangement of functional parts and supporting means in a variable resistor of the multiturn type.

Another object of the invention is to provide a compact arrangement of components of a variable resistor of the helical-element type, whereby a very small and lightweight, but strong resistor possessing excellent mechanical and electrical characteristics lis provided.

Other objects of the invention will hereinafter be set out in the appended claims or made evident in the following detailed disclosure of the preferred exemplary physical embodiment of the invention as illustrated in the accompanying drawings, in which drawings:

FIGURE 1 is an isometric view of an exemplary variable resistor according to the invention, on a grossly enlarged scale and with some parts displaced to better illustrate details;

FIGURE 2 is a longitudinal sectional view of structure depicted in FIGURE 1, on a further enlarged scale;

FIGURE 3 is a transverse sectional view of the variable resistor depicted in FIGURE 1, taken as indicated by broken line 3-3 irl FIGURE 2;

FIGURE 4 is a fragmentary view of certain components of the aforementioned exemplary Variable resistor, in partially disassembled relationship;

FIGURE 5 is an isometric view showing certain components of the exemplary variable resistor in partially disassembled array, with portions broken away to reveal details of construction; and i FIGURE 6 is a transverse sectional View of the exemplary variable resistor, the section being taken as indicated by broken line 6 6 in FIGURE 2.

Referring to the drawings, it is to be noted that all of the figures are drawn to greatly enlarged scale which is not necessarily uniform throughout the several views. Due to the very small size of the device (housing size of an exemplary model is 5M x Lrym x 1), gross enlargement of full-scale drawings is necessary in the interest of legibility and clarity of disclosure.

With reference to FIGURE 1 in particular, the exemplary variable resistor, 10, comprises a housing 12 of rectangular cross-section (preferably square, as shown) and of elongate generally box-like configuration, the length being proportioned according to the number of turns or convolutions of the helical resistance element. In the illustrated embodiment the resistance element is of such length as to provide ten full electrically effective turns of resistive material between terminals, and hence the element is of somewhat greater length. As indicated in FIGURE 2, the housing in preferred form comprises a central principal member in the form of a hollow body 12a and first and second end members 12b and I2C, respectively. As indicated in FIGURE 3, the housing 12 is of substantially square exterior cross-sectional configuration, and the body 12a is hollow and of generally round interior conguration, but is provided with a spiral groove 12u (FIGURE 2) in the interior wall. End 12C of the housing is formed with a reduced inner portion dimensioned to closely t within the adjacent end of the interior of body 12a and to be secured to the body as by means of adhesive such as epoxy resin cement or the like. End 12b of the housing is similarly proportioned to fit with and be secured to body 12a. Thus the housing provides an elongate interior chamber in which operating parts may be supported and sealed for protection. As is made evident in FIGURE 3, the wall thickness of body tZa may be relatively thin along longitudinal areas 12d, 12e, 121 and 12g intermediate the longitudinal corners such as 12h, and resistance to bending of the housing is provided by making the body of square configuration and utilizing the material comprised in the longitudinallyextending somewhat triangular corner portions as interconnected beams. The hollow beam or column structure thus provided by body 12a is converted into a very strong rigid box structure when ends 12b and 12C are united with the body, and thus the housing structure is made amply strong despite being elongate and very small.

The elongate chamber 13 provided by housing 12 is defined by end walls and an intermediate wall of roughly cylindrical form. Secured to the interior wall of body 12a and reposing in the helical groove 12u is a helical resistance element 14 which preferably but not necessarily is in the form of a helix of insulated wire mound which is disposed a large number of turns of resistance wire, the resistance element per se being produced according to known procedures. The resistance element is preferably aixed to body 12a by means of adhesive, such as epoxy resin cement, applied along and adjacent to the areas of contact therebetween.

Terminal conductors 14n and 14h (FIGURES 1, 2 and 3) are connected to appropriate end portions of the resistive component of resistance element 14, as by welding 0r brazing, and are extended through appropriately located apertures formed in t'ne wall structure of housing body 12a; and the terminal conductors extend to the second end of the housing in appropriate solts 12s and 121 (FIGURE 1) and are brazed to terminals which extend through end 12C so the terminal connections thus provided are accessible for connection in a circuit. If insulated wire terminals are desired the terminal conductors 14a and 14b may be soldered to flexible leads, but, as shown the conductors are soldered to suitable rigid terminals, such as J-hooks 14j, 14j. Following installation and embedment of the terminal conductors in selfcuring resin, the slots 12s and 12t and conductors are preferably sealed, as by insulator strips 12m, 12u that are cemented in place with adhesive, whereby the terminals are protected and the apertures sealed and the apperance of the housing improved.

Housing end 12b is formed to serve the three functions of sealing the first end of the housing, providing moans for supporting the variable resistor on a panel or the like, and providing a bearing for a rotatable driving device by means of which rotation is imparted to movable components situated in the noted chamber. To those ends the end 12b may be formed as a metal or alloy bushing in the shape or form indicated, and provided with a stepped bore 12bb (FIGURE 2) coaxial with the axis of the resistance element, and provided with a threaded outer end 12bc for entry through a panel aperture and for reception of a locking washer (not shown) and a nut 12b/1. Rotatively supported in bore 12bb is a driving device 18. The driving device comprises a shaft 18a and a resilient plural-limbed clutch or driving member 18e that is affixed to the inner end of shaft 18a in a manner and by means made evident by FIGURES 2 and 5, after the shaft has been assembled in the bore 18bb. One or more O-rings such as 18s are provided in appropriate annular groove means in the exterior of shaft 18a, whereby the bore is sealed against passage of foreign material. Shaft 18a is preferably formed of metal such as stainless steel, and is formed for cooperation with a shaft-end or tool (a screwdriver, for example), whereby rotation may be imparted to the shaft by a manual operator or by a motor. The limbs of driving member 18o are dimpled to provide in a circular array a set of projecting elements 18C' (FIGURE 5). f

Mounted for rotation about the longitudinal axis of the helix of resistance element 14 is a generally cylindrical elongate rotor or carriage device (FIGURES 2 and 5). The carriage device 20 is in the form of a long tube 26a terminated at a first end with a disc-like head 20h, and having lirst and second elongate longitudinally-extending slots 20c and 26d for accommodation of a slider device presently to be described. The second end 2de of carriage device 20 is mounted and supported for rotation in an annular bearing groove 12C' formed at the inner face of end 12e of the housing. A thrust hearing ring 20f of self-lubricating material, polytetraiiuoroethylene for example, may be seated in the bottom of groove 12C to minimize friction effects. The rst, or head, end Zlib of the rotatable carriage is rotatably supported by an annular cylindrical bearing surface portion of the inner wall of the housing chamber, as indicated in FIGURE 2.

The disc-like head 2Gb of carriage device 20 is provided with an axial bore 29h, and at its outer at face with a set of clutch or driven elements which in the i1- lustrated preferred from is a yuniformly spaced set or array of radially-extending grooves 20g that are disposed and dimensioned to ybe complementary to the elements 18e' of member 18C. Thus head 2Gb with its set or array of grooves serves as a lirst or driven clutch instrumentality and member 18C with its set of projecting elements 18e serves as a second or driving clutch instrumentality. As is indicated in FIGURE 5, exemplary driving member 13e is provided with a non-circular aperture at its center for reception of a complementary projection formed at the inner end of the blank of driving device shaft Ilia, whereby positive drive of member 18e by the shaft is assured. As is evident, peening of the exposed inner end of the blank over a portion of the inner face of member 18C concurrently secures member ISC to the shaft for positive rotation by the latter, and retains the shaft 18a in bore 12bb. As indicated in FIG- URE 2, resilient member 18e is formed with a concavoconvex congu1ation,'and the dimensioning of the cooperating parts is such that with carriage device 20 free to rotate, torque applied to shaft 13a in either rotational direction is transmitted through the interengaging elements 13o and 20g, and carriage device 20 is rotated. However, when unusual resistance to rotation or counter torque is exhibited by the carriagedevice, as, for example, when a contact carrier presently to be described is stopped, projections 18C' of the resilient member 18e ride out of respective ones of grooves 20g and slide around and snap into next-adjacent ones of the grooves and, if rotation of the driving device is continued, repeat the described slipping and snapping action incident to disengagement and re-engagement. As the projections 18e' n snap into respective grooves an audible click or signal is produced, thus providing a sense-perceptible warning signal for the operator. Also, as rotation of shaft 18a is continued with the carriage restrained against further rotation, an intermittent counter torque may be sensed in a tool used to rotate the shaft, giving a tactile signal or indication that the carriage is no longer rotating.

As is indicated in FIGURE 2, there is a bare electrical bus or return conductor extending from the second end 12e of the housing toward the first end 12b, and disposed axially along and in the chamber of the housing. The conductor 22 is secured in place at end 12C by conductive anchorage to a return-conductor terminai 22! that is sealed in an aperture formed in end 12C, and at its other end by reposing in bore 20h termed in head 20h of the carriage. The conductor 22 is formed of stift material whereby it is rigid and maintains an axial disposition as shown.

Slidably disposed upon return conductor 22 and in the guideways provided by the longitudinal slots 20c and 20d of the carriage device, is a slider device 16. The slider device is constructed and arranged to be rotated by the carriage device incident to rotation of the latter, and to be translated along the chamber 13 and conductor 22 by engagement with the helical resistance element 14 during such rotation. Thus the slider device comprises a body portion 1b provided with a bore 16d dimensioned for a sliding fit with conductor 22, and iin or vane means disposed and dimensioned for sliding engagement with resistance element 14. The lin or vane means is preferably in the form of a pair of outwardly extending vanes 16e, 16f (FIGURE 4) formed integrally with body portion 16b and shaped and each dimensioned to act as a portion of a respective helical thread cooperable with a respective side of a portion of a convolution or coil of the resistance element 14. The body portion 16b of the slider device is provided with a generally rectangular crown 16k having opposed parallel planar faces 16m, 1611 (FIG- URE 4) arranged for sliding and guiding engagement with the side walls of slot 20c of the carriage device 20. Also the body portion 16bfof the slider device is provided with other generally parallel planar faces 16p, 16g (FIGURE 3) for similar guiding and sliding engagement with the side walls of slot 20d of the carriage device. Thus as the carriage device is rotated, the slider device is forced to rotate around the axis of conductor 22, and by engagement of vanes 16e and 16]c with the resistanceelement 14, is also forced to progress longitudinally along the conductor 22 and carriage device 20 toward one end or the other of chamber 13.

j A stop element 12s (FIGURE 2) is provided at the second end of chamber 13, either formed. as an integral part of end 12e of the housing, or secured thereto, and disposed in the helical path of a complementary portion of the inner end of slider device 16. Similarly, another stop element 12g (FIGURE6) is provided adjacent the first end of the housing and protruding into chamber 13 and into the helical path of a portion of slider device 16. Thus when driven to close proximity to either end of chamber 13 the slider device collides with or engages one or the other of the stop elements and is arrested, whereby any continued rotation of the driving device 18 results in slippage of the clutch means with audible and tactile indication that adjustment has proceeded to kan end of the range of adjustment of the instrument.

Carried by the body portion 1612 ofthe slider device and forming a conductive portion or component of the latter is a contact device constructed and arranged to brush or Wipe along and electrically interconnect the resistance element 14 and return conductor 22. The contact device, 16C, is preferably formed as an integral resilient conductor having an inner contact 16e and an outer contact 16e (FIGURE 2), formed or provided on first and second limbs of a reversely bent generally V-shaped resilient conductive strip as depicted in'FIGURE 4. The contact device is attached to the body portion 16b of the slider device by means of a pair of laterally projecting lugs or ears 16r (FIGURE 4) that are dimensioned to tightly tit in complementary notches 16r formed in the upper portionV of crown 16m. The first or inner limb of the contact device is arranged to be disposed in an elongate notch 16x (FIGURE 2) formed in the Wall of the bore of the slider body member, and the second or outer limb of the contact device is constructed and arranged to lie partly in an along a longitudinal recess 16y formed in the upper face of crown 16m of the slider body member 16b. As is made evident in FIGURE 2, the limbs of the contact device are brought toward each other from an open relaxed status, whereby they tend to move apart and thus press contact 16o into effective electrical contact with conductor 22 and contact 16e' into effective contact with the resistance element 14. Further, as the slider body portion 16b is rotated and concurrently translated by and incident to rotation of carriage device and engagement of the slider vanes with the helical guide formed by the element, outer contact 16C is caused to move in a helical path along an exposed contact surface or zone of the resistance element; the inner contact meanwhile moving along a helical contact path or zone on conductor 22. Thus the resistance exhibited between either of terminal members 16j and terminal member 22t is adjustable and the desired value is selected by rotation of driving device 18.

Several methods and means of electrically insulating those components requiring to be insulated are available and will be obvious to those skilled in the art. In the preferred embodiment or construction illustrated, the housing body 12a and end 12e are formed of insulation such as a rigid synthetic resin, and carriage device 2t) and the body portion 16b of slider device 16 are also formed of insulation such as resin-filled fiberglass or that material commercially sold under the trade name Nylatron It will be noted that there is a spatial gap between shaft 18a and the adjacent end of conductor 22, whereby the metallic driving device 18 is electrically isolated from the electrically active components. Preferably, but not necessarily, an insulative disc-like member 2th' is disposed in the gap as indicated. The insulative disc-like member is preferably formed with a portion fitting in bore 20h of the head of the carriage, as shown, and the member may be press-fitted or cemented in place on and to the head of the carriage.

The preceding description makes it evident that there has been attained by the invention a multi-turn (helical element) variable resistor which by the arrangement and construction of components is of very small size but which is exceptionally rugged and resistant to physical abuse and which fully attains the aforementioned objects. It is evident that in the light of the foregoing disclosure of a specific exemplary embodiment of the invention, changes within the true spirit and scope of the invention will occur to others, and accordingly it is not desired to limit the invention to the specific details of the exemplary embodiments, but we claim:

l. A variable resistor comprising:

rst means, including an elongate hollow housing providing an elongate chamber therein bounded at the ends thereof by first and second end walls, and including means providing coaxial bearing means at the ends of said chamber;

second means, including a helical resistance element presenting a plurality of convolutions disposed about a linear axis longitudinally of said chamber and affixed to said housing in said chamber, and electrical terminal connections to electrical ends of said element extending to the exterior of said housing;

third means, including an elongate longitudinally-slotted rotatable carriage device disposed in said chamber for rotation about said linear axis of said resistance element, said carriage device having bearing surfaces arranged for rotation in said bearing means and having an end face presenting a first set of clutch elements;

fourth means, including an elongate conductor disposed along said axis in said chamber and insulated from said element, and including a terminal for said conductor extending to the exterior of said housing at said second end wall;

fifth means, including a rotary driving device journaled at said iirst end wall, said driving device comprising a set of clutch elements positioned for cooperative driving engagement with said first set of clutch elements, and said driving device having an end accessible from outside said housing; and

sixth means, comprising a slider device having insulated guide surfaces engaging said resistance element for traverse therealong incident to rotation about said axis and having guide surfaces engaging said carriage device along a slot thereof for rotation therewith and thereby about said axis, and said slider device comprising contact means in brushing electrical contact with said elongate conductor and with said resistance element to electrically connect the said conductor lto said element;

whereby upon continued rotation of said driving device said slider device is rotated and thereby is driven along said carriage device to an end of said chamber until such motion is arrested at that end of the chamber and thereafter slipping of said sets of clutch elements occurs, to thereby avoid damage to said car.- riage device, slider device, contact, and resistance element.

2. A variable resistor according to claim l, in which said housing is of insulative material and of substantially square external cross-section and in which said electrical terminal connections extend through and out of said second end wall.

3. A variable resistor according to claim l, in which said carriage device is of generally cylindric configuration and is provided with an axial bore and diametrically opposed open elongate apertures forming the longitudinal slots thereof.

4. A variable resistor according to claim l, in which said slider device comprises an insulative block having a longitudinal bore receiving said elongate conductor, said block having a pair of radially-extending vanes providing said insulated guide surfaces engaging said resistance element, and in which said contact means is secured to said block and comprises two resilient contact arms one of which projects inwardly into engagement with said conductor and the other of which projects outwardly into engagement with said resistance element.

5. For a multi-turn helical-element variable resistor having an elongate housing having ends providing bearing means and having a resistance element of helical configuration and iirst and second end terminals therefor, resistance-adjusting mechanism comprising:

an elongate longitudinally-slotted generally cylindrical carriage device having lirst and second ends and hav* ing a longitudinal axis substantially coincident with the axis of said resistance element, said carriage having ends arranged to be rotatably supported by respective ones of the bearing means of the housing and having longitudinally-extending guide surfaces, and said bearing means supporting the carriage device for rotation about said axis, an elongate exposed electrical conductor having first and second end portions and arranged coaxial with said carriage device with one end portion disposed to be firmly supported by one of the ends of the housing, and the other end portion connected to and supported by one end of said carriage device for relative rotation therebetween and said conductor being disposed in part within said carriage device; and

a slider device mounted on said conductor for longitudinal movement along said carriage device and having complementary guide surfaces cooperating with said longitudinally-extending guide surfaces of said carriage device, said slider device including contact means comprising first and second electrically connected contacts, the first of which extends outwardly for engagement with a helical resistance element and the second of which extends inwardly into brushing electrical engagement with said elongate exposed electrical conductor.

6. A structure according to claim 5, in which said slider device includes an insulative block having a bore therethrough receiving said elongate exposed electrical conductor.

7. A structure according to claim 6, in which said contact means is a reversely-bent resilient strip having iirst and second free limbs each terminated by a respective one YJ f said contacts and having an intermediate portion attached to said slider device.

8. A n elongate very small multi-turn variable resistor comprrsmg:

first means, including an elongate housing having first and second ends and comprising bearing means at each end thereof, said housing providing an elongate enclosed chamber bounded by first and second end walls provided by said ends and by at least one other wall having spaced-apart portions equidistant from 'a longitudinal axis extending through the chamber; second means, comprising an electrical conductor disposed along said axis in said chamber said conductor being iixedly supported at one end of said housing by said housing and being supported adjacent the other end of said housing against movement transversely of said axis; third means, comprising an elongate carriage device disposed in said chamber and rotatable about said axis upon said bearing means at both ends of said housing, and an insulative slider device slidably mounted for rotation upon and translation along said conductor and having interengagement with said carriage device for rotation by said carriage said slider device having outwardly-extending vane means and carrying contact means including a first contact brushing on said conductor and a second contact electrically connected to said first contact and extending outwardly away from said contact-carrier and said conductor; f fourth means, comprising a helical resistance of at least two convolutions and arranged coaxially with respect to said carriage device, said resistance element being affixed to said housing in said chamber and disposed for engagement by said vane means for causing longitudinal translation of said slider device in said chamber incident to rotation of the latter about said axis; fifth means, comprising electrical terminal means for electrical ends of said resistance element and for said electrical conductor; and sixth means, including driving means accessible from the exterior of said housing and connected to said carriage device for imparting rotation to said carriage device. f 9.. A variable resistor according to claim 8, said carriage device including at one end thereof a first clutch means and said driving means including a second clutch means in driving engagement with said first clutch means, and stop means supported by said housing and disposed for engagement by said contact-carrier at respective ends of traversal thereof longitudinally of said chamber,

whereby when said contact carrier reaches either extreme of traversal along said chamber further movement thereof in the same direction is prohibited and further operation of said driving means in the same direction is accommodatedby slippage between sai first and second clutch means. l0. A variable resistor comprising: first means including a very small elongate housing of square external cross-section providing an elongate interior chamber of substantially circular cross-section bounded by four longitudinal generally triangular corner strut portions interconnected by longitudinal thin-wall portions, said housing having first and second ends providing end walls for said chamber and said first means providing first and second bearing means at said ends; second means, comprising an electrical return conductor disposed along the longitudinal axis of said chamber and affixed` at one end of said chamber to one end wall of said housing and said conductor having an external terminal connection thereto; third means, comprising a helical resistance element of a plurality of convolutions disposed in said chamber in said housing coaxially with said return conductor,

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of said resistance element accessible for external connection; fourth means, comprising an elongate rotatable carriage device in said chamber journaled at its ends in said bearing means, arranged coaxially with said return conductor and generally between said conductor and said resistance element and in close proximity to both; fifth means, comprising a slider device slidably engaging said carriage device and said conductor for support thereby and longitudinal translation therealong and rotation by and with said carriage device, said slider device comprising means engaged with said resistance element and means engaged with said return conductor whereby said return conductor is elecl trically connected to said resistance element at a point adjacent the slider device and whereby the slider device is traversed along both said return conductor and said resistance element incident to relative rotation between said slider device and said resistance element; and

sixth means, comprising a rotary driving device including means accessible from outside said housing, for effecting rotation of said carriage device.

ll. A variable resistor according to claim l0, in which said driving device is disposed at one end of said housing and in which the several said terminal connections extend outwardly through the opposite end of said housing.

l2. A variable resistor according to claim l1, in which said carriage device and said driving device comprise interacting clutch elements effective to transmit normal driving torque to said carriage device from said driving device and effective to permit relative rotation therebetween incident to arrestment of rotation of said carriage device.

13. A variable resistor according to claim l2, said housing comprising means for arresting rotation of said slider device at either extremity of the range of movement of the slider device along said carriage device in said chamber; and means for sealing said housing against ingress of foreign material.

14. A variable resistor comprising:

first means, including an elongate housing providing an elongate enclosed chamber of substantially circular cross-section and having a longitudinal axis along the longitudinal center of the chamber, said Ahousing including first and second ends defining end walls of said chamber and said first means including coaxially aligned bearing means at said ends of said housing;

second means, including an elongate electrical return conductor disposed along the axis of said chamber and fixed to said second end of said housing and having a terminal connection extending to the exterior of said housing;

thirdmeans, including a helical resistance element of a plurality of convolutions disposed in said chamber coaxially with said return conductor and having respective terminal connections to electrical ends of the element, said connections extending to the exterior of saidhousing; and l fourth means, including elongate rotary means rotatably supported at both ends thereof by said bearing means and arranged for rotation about a longitudinal axis coincident with said first named axis, said rotary means comprising an elongate carriage of generally cylindrical configuration disposed around and along said return conductor and supporting said conductor adjacent the lirst end of said housing and said rotary means being encircled by said resistance element, and further comprising a slider device slidable along said return conductor and rotated by said elongate carriage and engaging and electrically interconnecting said return conductor and said resistance element to vary the resistance exhibited between said first lL i named terminal connection and another of said terminal connections.

15. A variable resistor comprising:

first means, including an elongate housing providing an elongate enclosed chamber of substantially circular cross-section and having a longitudinal axis along the longitudinal center of the chamber, said housing including first and second ends defining end walls of said chamber and said first means including coaxially aligned bearing means at said ends of said housing;

second means, including an elongate electrical return conductor disposed along the axis of said chamber and fixed to said second end of said housing and having a terminal connection extending to the exterior of said housing;

third means, including a helical resistance element of a plurality of convolutions disposed in said chamber coaxially with said return conductor and having respective terminal connections to electrical ends of the element, said connections extending to the exterior of said housing; and

fourth means, including7 elongate rotary means rotatably supported at both ends thereof by said bearing means and arranged for rotation about a longitudinal axis coincident with said first named axis, said rotary means comprising an elongate carriage of generally cylindrical configuration disposed around and along said return conductor and supporting said conductor adjacent the first end of said housing and said rotary means being encircled by said resistance element, and further comprising a slider device slidable along said return conductor and rotated by said elongate carriage and engaging and electrically interconnecting said return conductor and said resistance element to vary the resistance exhibited between said first named terminal connection and another of said terminal connections, said slider device comprising an insulative body and a resilient conductive contact device supported with conductive contacts thereof in contact with said resistance element and said return conductor, said insulative body having a bore in which said return conductor is slidably received whereby said conductive contacts press substantially uniformly on said resistance element throughout traverse therealong.

16. A variable resistor according to claim l5, in which said contact device comprises a V-shaped strip the limbs of which constitute, respectively, an inwardly-extending limb and contact brushing on said return conductor and an outwardly-extending limb and contact brushing on said resistance element.

17. A multi-turn helical-element variable resistor having an elongate slender housing having first and second ends and two sets of elongate substantially parallel planar exterior faces between said ends and defining an elongate chamber of substantially circular cross-section, permitting arrangement of a plurality of like variable resistors in a compact array of resistors in tiers and layers in a minimum of space, and a helical resistance element disposed in said housing, said variable resistor also comprising:

first means, including a longitudinally-extending electrical return conductor disposed along the longitudinal axis of said housing and anchored therein at said second end of said housing and supported adjacent the first end of the said housing against dispacement transversely of said axis;

second means, including terminal connections for said resistance element and said return conductor, extending outwardly from said second end of said housing and having respective electrical connection to said resistance element iand said return conductor; third means, including mounting means at said first end of said housing and disposed within a space bounded by extended continuations of the planes of said planar faces, for securing said housing to a panel at an aperture therein; and fourth means, including rotary means disposed for rotation in said housing and supported thereby around the longitudinal axis of the housing and accessible for application of driving torque outside of said housing, for variably electrically interconnecting said resistance element and said return conductor, whereby a plurality of like variable resistors may be arranged in such array in a minimum of space and Without waste of intervening space.

18. A very small variable resistor comprising:

first means, including an elongate housing providing an enclosed elongate chamber and a helical resistance element of a plurality of convolutions disposed with the axis of the helix thereof longitudinally of said chamber and said housing having first and second end poitions each provided with a respective one of two coaxial bearing means and said first end portion having a bore therethrough substantially coaxial with said resistance element, said housing comprising fixed stops at respective ends of said chamber, and said resistance element having terminal connections thereto extending to the exterior of said housing;

second means, including rotary means including a slotted carriage means in said housing and a return conductor disposed along said axis, said rotary means including a rotatable sliding contact device riding on said conductor and in the slots of said carriage to move said contact along said resistance element incident to rotation of said rotary means and said Contact device including means to electrically interconnect said contact and said return conductor, said carriage means being journaled for rotation about said axis in said chamber in said bearing means and said rotary device having a first set of clutch elements arranged about said axis, said rotary means being subject to arrestment of by continued rotation thereof in either direction; and

third means, including a rotary driving device journaled in said housing at said bore for rotation about said axis and comprising a second set of clutch elements arranged about said axis in cooperative driving relationship with said first set of clutch elements, one set of said sets of clutch elements comprising resilient means inducing very rapid re-engagement of the sets of clutch elements incident to rotation following disengagement, andthe other set thereof being formed and arranged to cause re-engagement to be very rapid, whereby continued rotation of said rotary driving device following arrestment of said rotary means causes production of an audible signal by said clutch elements.

19. A very small slender elongate multi-turn helicalelement potentiometer adapted to be secured at one end thereof to supporting structure and adapted to be mounted in face to face contact with like potentiometers in tiers and rows, said potentiometer being characterized by exceptional longitudinal stiffness and exceptional immunity to adverse` effects incident to being subjected to severe vibration, said potentiometer comprising:

first means, including a slender elongate housing means of rectangular exterior cross-section and of generally circular interior cross-section and having first and second ends and defining a generally cylindrical chamber, said housing means including a body portion comprising four longitudinally-extending corner portions of generally triangular cross-section interconnected along the lengths thereof by longitudinally-extending thin wall portions, said ends and body portion forming a strong rigid slender elongate box-like structure and said housing means providing at the ends thereof first and second coaxial bearing means;

second means, including a multi-turn helical resistance element disposed in said chamber in coaxial relation to said bearing means, and said second means including external terminal connections to said resistance element;

third means, including a stiff electrical conductor disposed along the center of said chamber and aixed to the first end of said housing;

fourth means, including stiff slender elongate rotary means in said chamber journaled in said bearings and including means adjacent saidiirst end of said n housing for supporting one end portion of said electrical conductor against lateral displacement, said fourth means contributing materially to the longitudinal stiffness of said potentiometer, and said fourth meansv comprising means rotatable therewith for electrically interconnecting said conductor to ya selected part of said resistance element; and

fifth means, comprising driving means at said second end of said housing, for application of driving torque to said elongate rotary means to cause rotation thereof and adjustment of the potentiometer.

References Cited in the file of this patent UNITED STATES PATENTS Coultas et a1. Apr. 5, 1932 Schellenger Dec. 3l, 1935 Lewis June 12, 1945 Smith etal -..d May 19, 1959 Moore et al Nov. 22,` 1960 Habereder July 30, 196,3

v FOREIGN PATENTS v Australia Feb. 22, 1960 

14. A VARIABLE RESISTOR COMPRISING: FIRST MEANS, INCLUDING AN ELONGATE HOUSING PROVIDING AN ELONGATE ENCLOSED CHAMBER OF SUBSTANTIALLY CIRCULAR CROSS-SECTION AND HAVING A LONGITUDINAL AXIS ALONG THE LONGITUDINAL CENTER OF THE CHAMBER, SAID HOUSING INCLUDING FIRST AND SECOND ENDS DEFINING END WALLS OF SAID CHAMBER AND SAID FIRST MEANS INCLUDING COAXIALLY ALIGNED BEARING MEANS AT SAID ENDS OF SAID HOUSING; SECOND MEANS, INCLUDING AN ELONGATE ELECTRICAL RETURN CONDUCTOR DISPOSED ALONG THE AXIS OF SAID CHAMBER AND FIXED TO SAID SECOND END OF SAID HOUSING AND HAVING A TERMINAL CONNECTION EXTENDING TO THE EXTERIOR OF SAID HOUSING; THIRD MEANS, INCLUDING A HELICAL RESISTANCE ELEMENT OF A PLURALITY OF CONVOLUTIONS DISPOSED IN SAID CHAMBER COAXIALLY WITH SAID RETURN CONDUCTOR AND HAVING RESPECTIVE TERMINAL CONNECTIONS TO ELECTRICAL ENDS OF THE ELEMENT, SAID CONNECTIONS EXTENDING TO THE EXTERIOR OF SAID HOUSING; AND FOURTH MEANS, INCLUDING ELONGATE ROTARY MEANS ROTATABLY SUPPORTED AT BOTH ENDS THEREOF BY SAID BEARING MEANS AND ARRANGED FOR ROTATION ABOUT A LONGITUDINAL AXIS COINCIDENT WITH SAID FIRST NAMED AXIS, SAID ROTARY MEANS COMPRISING AN ELONGATE CARRIAGE OF GENERALLY CYLINDRICAL CONFIGURATION DISPOSED AROUND AND ALONG SAID RETURN CONDUCTOR AND SUPPORTING SAID CONDUCTOR ADJACENT THE FIRST END OF SAID HOUSING AND SAID ROTARY MEANS BEING ENCIRCLED BY SAID RESISTANCE ELEMENT, AND FURTHER COMPRISING A SLIDER DEVICE SLIDABLE ALONG SAID RETURN CONDUCTOR AND ROTATED BY SAID ELONGATE CARRIAGE AND ENGAGING AND ELECTRICALLY INTERCONNECTING SAID RETURN CONDUCTOR AND SAID RESISTANCE ELEMENT TO VARY THE RESISTANCE EXHIBITED BETWEEN SAID FIRST NAMED TERMINAL CONNECTION AND ANOTHER OF SAID TERMINAL CONNECTIONS. 